COMMITMENTS AND CONTINGENCIES (Narrative) (Details) - USD ($) $ in Millions	12 Months Ended
	Dec. 31, 2018	Dec. 31, 2017	Dec. 31, 2016
Commitments
Letters of credit outstanding	$ 15.3	$ 13.8
Amount of outstanding surety bonds	101.2	88.5
Contractual rental expense, including participation rent	9.7	$ 8.6	$ 8.4
Guarantee Obligations | Downtown columbia
Commitments
Guarantee amount	$ 1.0